The present invention discloses novel improvements to a word processor described and illustrated in U.S. PAT. NO. 4,244,031 which is assigned to the same assignee as this application. Prior art devices of comparable function comprise automatic typewriters which allow editing of input data subsequent to playback. More specifically, the typist types in the data for printing and backspaces and types over to correct mistakes. Then, a button is depressed and the entire page is automatically printed or typed in corrected form.
Such an automatic typewriter, while allowing efficient correction of mistakes, suffers from several disadvantages. The page, while being initially typed, becomes cluttered and hard to read if there are a number of typeovers. This increases the possibility for error. It is not difficult to overlook a typographical error on a cluttered page and such an error requires correction and a second playback to produce an errorless copy. Another disadvantage of the typical automatic typewriter is slow operating speed. The typewriter may not be used to compose another page until the playback or printing of the first page is completed.
Another prior art device comprises a cathode ray tube which displays an entire page of printed characters. Subsequent to composing and correction of errors on the screen, that is, only after composition and correction of errors of the entire page, the entire page is printed. These systems suffer from the same drawback in that the display is inaccessible during printing.
Another drawback of such systems is that the display does not correspond to the printed page under some circumstances. In cases where the backspace and typeover functions, for example, are used to produce a Japanese Yen symbol ( ) by superimposing an equal sign(=) on the capital letter (Y), the position of subsequent data on the display does not correspond to the data as printed. This is because the printer has various control functions which are not provided to the display.
Such prior art word processors suffer from yet further drawbacks regarding margin release and right justification. In order to release the right or left margin to input data rightwardly or leftwardly thereof respectively, it is necessary to reposition the margin marks on the display, or in effect reset the margins. This operation is slow and inefficient.
Right justification, or alignment of the right end of the line of data with the right margin to obtain a straight right side of the printed data, has heretofore been possible only when the unjustified right end of the line is leftward of the right margin. Justification is accomplished by increasing the width of blank data spaces between characters in proportion to the distance from the end of the line of data to the right margin. Right justification has heretofore been impossible where the line has extended rightward of the right margin due to a right margin release operation.
It has been proposed to define a "hot zone" extending leftwardly from the right margin and automatically terminate data entry and initiate printing of the line when a hyphen or space is detected in the hot zone. This facilitages automatic right justification. However, it is sometimes awkward to hyphenate or terminate a word in the hot zone, but quite advantageous to enter the entire word so that it extends several spaces past the right margin. Prior art word processors do not allow right justification under these conditions.